《windows程序设计》滚动条中WM_SIZE消息问题
ztwz 2005-04-15 11:47:55 下面这些代码是书中自带的。问题我注释在//后面了。
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static int cxChar, cxCaps, cyChar, cxClient, cyClient, iMaxWidth ;
HDC hdc ;
int i, x, y, iVertPos, iHorzPos, iPaintBeg, iPaintEnd ;
PAINTSTRUCT ps ;
SCROLLINFO si ;
TCHAR szBuffer[10] ;
TEXTMETRIC tm ;
switch (message)
{
case WM_CREATE:
hdc = GetDC (hwnd) ;
GetTextMetrics (hdc, &tm) ;
cxChar = tm.tmAveCharWidth ;
cxCaps = (tm.tmPitchAndFamily & 1 ? 3 : 2) * cxChar / 2 ;
cyChar = tm.tmHeight + tm.tmExternalLeading ;
ReleaseDC (hwnd, hdc) ;
iMaxWidth = 40 * cxChar + 22 * cxCaps ;
return 0 ;
////////////////////////////////////////////////////////////////////////////////
//书中说WM_SIZE消息是在客户区大小被改变时调用,难到滑动滚动条也有WM_SIZE消息?
//在这个程序中是什么事件引起windows发送WM_SIZE消息的?
///////////////////////////////////////////////////////////////////////////////////////
case WM_SIZE:
cxClient = LOWORD (lParam) ;
cyClient = HIWORD (lParam) ;
// Set vertical scroll bar range and page size
si.cbSize = sizeof (si) ;
si.fMask = SIF_RANGE | SIF_PAGE ;
si.nMin = 0 ;
si.nMax = NUMLINES - 1 ;
si.nPage = cyClient / cyChar ;
SetScrollInfo (hwnd, SB_VERT, &si, TRUE) ;
// Set horizontal scroll bar range and page size
si.cbSize = sizeof (si) ;
si.fMask = SIF_RANGE | SIF_PAGE ;
si.nMin = 0 ;
si.nMax = 2 + iMaxWidth / cxChar ;
si.nPage = cxClient / cxChar ;
SetScrollInfo (hwnd, SB_HORZ, &si, TRUE) ;
return 0 ;
case WM_VSCROLL:
// Get all the vertial scroll bar information
si.cbSize = sizeof (si) ;
si.fMask = SIF_ALL ;
GetScrollInfo (hwnd, SB_VERT, &si) ;
// Save the position for comparison later on
iVertPos = si.nPos ;
switch (LOWORD (wParam))
{
case SB_TOP:
si.nPos = si.nMin ;
break ;
case SB_BOTTOM:
si.nPos = si.nMax ;
break ;
case SB_LINEUP:
si.nPos -= 1 ;
break ;
case SB_LINEDOWN:
si.nPos += 1 ;
break ;
case SB_PAGEUP:
si.nPos -= si.nPage ;
break ;
case SB_PAGEDOWN:
si.nPos += si.nPage ;
break ;
case SB_THUMBTRACK:
si.nPos = si.nTrackPos ;
break ;
default:
break ;
}
si.fMask = SIF_POS ;
SetScrollInfo (hwnd, SB_VERT, &si, TRUE) ;
GetScrollInfo (hwnd, SB_VERT, &si) ;
if (si.nPos != iVertPos)
{
ScrollWindow (hwnd, 0, cyChar * (iVertPos - si.nPos),
NULL, NULL) ;
UpdateWindow (hwnd) ;
}
return 0 ;
case WM_HSCROLL:
si.cbSize = sizeof (si) ;
si.fMask = SIF_ALL ;
GetScrollInfo (hwnd, SB_HORZ, &si) ;
iHorzPos = si.nPos ;
switch (LOWORD (wParam))
{
case SB_LINELEFT:
si.nPos -= 1 ;
break ;
case SB_LINERIGHT:
si.nPos += 1 ;
break ;
case SB_PAGELEFT:
si.nPos -= si.nPage ;
break ;
case SB_PAGERIGHT:
si.nPos += si.nPage ;
break ;
case SB_THUMBPOSITION:
si.nPos = si.nTrackPos ;
break ;
default :
break ;
}
si.fMask = SIF_POS ;
SetScrollInfo (hwnd, SB_HORZ, &si, TRUE) ;
GetScrollInfo (hwnd, SB_HORZ, &si) ;
if (si.nPos != iHorzPos)
{
ScrollWindow (hwnd, cxChar * (iHorzPos - si.nPos), 0,
NULL, NULL) ;
}
return 0 ;
case WM_PAINT :
hdc = BeginPaint (hwnd, &ps) ;
si.cbSize = sizeof (si) ;
si.fMask = SIF_POS ;
GetScrollInfo (hwnd, SB_VERT, &si) ;
iVertPos = si.nPos ;
GetScrollInfo (hwnd, SB_HORZ, &si) ;
iHorzPos = si.nPos ;
iPaintBeg = max (0, iVertPos + ps.rcPaint.top / cyChar) ;
iPaintEnd = min (NUMLINES - 1,
iVertPos + ps.rcPaint.bottom / cyChar) ;
for (i = iPaintBeg ; i <= iPaintEnd ; i++)
{
x = cxChar * (1 - iHorzPos) ;
y = cyChar * (i - iVertPos) ;
TextOut (hdc, x, y,
sysmetrics.szLabel,
lstrlen (sysmetrics.szLabel)) ;
TextOut (hdc, x + 22 * cxCaps, y,
sysmetrics.szDesc,
lstrlen (sysmetrics.szDesc)) ;
SetTextAlign (hdc, TA_RIGHT | TA_TOP) ;
TextOut (hdc, x + 22 * cxCaps + 40 * cxChar, y, szBuffer,
wsprintf (szBuffer, TEXT ("%5d"),
GetSystemMetrics (sysmetrics.iIndex))) ;
SetTextAlign (hdc, TA_LEFT | TA_TOP) ;
}
EndPaint (hwnd, &ps) ;
return 0 ;
case WM_DESTROY :
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}